Recently, a conductive film has been developed in which a mesh pattern made up wires is disposed on a transparent substrate. The conductive film can be used as an electrode or a heat-generating sheet. Not only can such a conductive film be used as an electrode for a touch panel, or an electrode for an inorganic EL element, and organic EL element or a solar cell, but the conductive film may also be applied to a portion of a defroster (defrosting device), a window glass of a vehicle, etc., for example.
Depending on the use of the aforementioned various products, cases are known to occur in which such a mesh pattern produces considerable granular noise, which obstructs the visibility of objects to be observed. Various techniques have been proposed in which, by arranging the same or different mesh patterns in a regular or irregular manner, such granular noise is suppressed, whereby the visibility of objects to be observed can be improved.
For example, in Japanese Laid-Open Patent Publication 2009-094467, an image display device is disclosed having an electromagnetic shielding film and a moire (moiré) preventing film attached thereto, wherein the electromagnetic shielding film has a conductive portion and an opening portion, and the moire preventing film has a moire preventing part (see paragraph [0063], and FIGS. 1, 10A and 10B of the patent publication). As a result of this structure, localized increases of an integrated amount of transmitted light are suppressed, and a nearly constant integrated amount can be realized over the entirety of the film. In other words, by combining the conductive portion and the opening portion, potential formation of mesh patterns is eliminated, making it difficult for moire patterns to occur.
Further, in Japanese Laid-Open Patent Publication 2009-117683, a device and a method are disclosed in which two-dimensional power spectra are calculated respectively in relation to image data representing a pixel array pattern and an electromagnetic wave shielding pattern, and the shape of the electromagnetic wave shielding pattern is determined such that the difference in spatial frequency corresponding to peaks thereof exceeds a predetermined value (see paragraphs [0014] and [0024] of the patent publication). Consequently, generation of moire patterns can be suppressed, whereby an increase in surface resistivity and degradation in transparency can be avoided.
Furthermore, as shown in FIG. 33A, according to Japanese Laid-Open Patent Publication No. 2009-137455, a window for a riding movable body and the shape of a pattern PT1 thereof in plan view are disclosed, having a mesh layer 4, in which rounded arcuate conductive wires 2 from which portions have been cutout are arranged repeatedly in a lattice shape, and respective ends of the arcuate wires 2 are connected to the vicinity of a center portion of another adjacent arcuate wire 2 (see paragraph [0029] and FIG. 3 of the patent publication). In accordance therewith, it is noted that not only visibility but also shielding of electromagnetic waves as well as resistance to breakage can be improved.
Further, as shown in FIG. 33B, according to Japanese Laid-Open Patent Publication No. 2009-016700, a transparent conductive substrate and the shape of a pattern PT2 thereof as viewed in plan are disclosed, which is manufactured using a solution, i.e., a self-organized metal particle solution, which forms a mesh-like structure naturally on the substrate if one side of the substrate is coated and then left untreated (see paragraphs [0022] to [0024] and FIG. 1 of the patent publication). In accordance therewith, it is noted that an irregular mesh-like structure can be obtained in which moire phenomena do not occur.
Moreover, as shown in FIG. 33C, according to Japanese Laid-Open Patent Publication No. 2009-302439, a light transmissive electromagnetic shield material and the shape of a pattern PT3 thereof as viewed in plan are disclosed, in which an electromagnetic shield layer 6 has a sea region structure in a sea-island configuration, wherein the shapes of island regions 8 made up from openings surrounded by the electromagnetic shield layer 6 differ mutually from each other (see paragraphs [0011] to [0015] and FIG. 1(B) of the patent publication). In accordance therewith, it is noted that both optical transparency and electromagnetic shielding are improved without the occurrence of moire patterns.